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Hi, what can be causing these lines in the slip casted piece?

I bought the slip already mixed, but it wasn't newly made so it was rather thick.

Measured the specific gravity to 1.82 and have been adding water to make it more fluid.

Made some bowls in an open one piece mold and sometimes these lines showed, sometimes not. They were always on the outside, against the mold.

Now I'm trying a two piece mold and added more water because I had trouble filling the whole mold. And now these lines are more accentuated.

Anyone knows what they are called and why I get them?

 

 

IMG_20200629_205222080~2.jpg

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You shuld not just add water to  make more to fill the mold slip it takes some darvan 7 as well as water-read up on slip making-its more complex than just adding water. . You need it to be the right specific gravity and flow rate. Those lines look like drying lines of some sort. its had to tell one cannot see the whole form just a small section?

how did you fill the mold -fast or slowly?Was the mold dry?Lots of factors

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Okej, I was hoping that water would be enough since the specific gravity was a bit high to start with.

I fill the mold with this funnel, and since the holes are rather small it fills slowly.

The mold has been drying and today was the first day I used it, and it was really dry.

In the image below there was a problem where the slip wouldn't flow from one hole to the other, so I had to fill it from both holes.

That's why it has that "valley" in the middle. But it shows the lines that I am talking about clearer.

form.jpg.e689633b8dc59fcd57cc1d74c8344c4b.jpg

över.jpg

under.jpg

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My guess is the fill holes are to small-the funnel fills so slowly the slip is drying as it fills leaving the lines-make the fill hole larger-adjust the slip so its the right specific gravity. make sure you can fill it faster than a slow small funnel end.

Get the slkip right try again if same issue then enlarge those holes-should work much better.

 

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I think they're like the lines the tide leaves on a sandy beach.  You need to pour so the slip hits the same spot all the way through.  

I can't get my head round your mould.  Is the mould wavy and the smaller lines are the problem?  The red circled area?

image.png.f8e4239ca835aaed7fc899c6eaea2e7e.png

 

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The mold is a small square dish-the spur(fill) holes are in the foot and there are two small holes there. Its filled upside down. The wavy design is carried thu the outer mold edge (which is the odd looking part).

With the the thick slip and the tiny fill holes the slip is drying as fast as it getting slowly dripped into mold I think-leaving the lines.

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You are quite right, the waves are there by design, the lines you have marked red are the problem.

I think Mark and Liam are correct thinking that my slip needs more deflocculant to get the viscosity right.

The slip definitely hits the same spot all the time because I pour it through the funnel.

Here's an image showing the whole plate, this one didn't have so much trouble with those lines.

IMG_20200701_150726_293.jpg

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